Alzheimer's disease (AD) belongs to a group of neurodegenerative disorders and causes cognitive, memory and behavioral impairments. The hallmarks of Alzheimer's disease include extracellular amyloid plaques, intraneuronal neurofibrillary tangles, neuronal dysfunction and ultimately brain atrophy. The risk for developing AD increases with age and with increased number of persons reaching high age, a condition with increasing impact on the quality of life for elderly people. In addition the society faces a situation with accelerating costs.
In spite of the fact that the disease has been known for many years and several suggestions for treatment have been made, even today, there is no such efficient disease modifying therapy available today but only drugs which at best may provide symptomatic treatment. The mechanism behind the disease has been subject to a lot of studies. Briefly, Aβ for some reason starts to aggregate and via several intermediate forms, finally produces insoluble fibril/plaque deposits in the brain. It was early believed that the plaques, as such, affect the neurons and the signals transmitted by these, but today the results of the extensive studies indicate that soluble, aggregated, intermediate forms of Aβ most likely are a major cause of the disease and the symptoms observed in the patients.
One such intermediate form in the cascade of aggregated forms from Aβ monomers to insoluble Aβ fibrils is the soluble, high molecular weight Aβ protofibril, which was first described by Walsh in 1997 in The Journal of Biological Chemistry (Vol. 272(35) p. 22364-72). The importance of the Aβ protofibril for the development of AD was identified by the group of scientists headed by Lars Lannfelt, Uppsala University, in their studies of the Arctic mutation, which is an E693G mutation in the amyloid precursor protein (APP) causing increased formation of Aβ protofibrils. A family in northern Sweden carrying this mutation was found to develop severe Alzheimer's disease early in life and the finding of this combination provided the basic ideas for a new therapy. Accordingly, the Aβ protofibril was identified as strongly related to the disease and an important target for therapy. Based on their studies with Aβ peptides comprising the Arctic mutation, Lannfelt et al were able to produce Aβ protofibrils in vitro, Arctic as well as wild-type, in sufficient amounts for immunization and subsequent selection of antibodies with high affinity for Aβ protofibrils compared to other species in the Aβ system. Examples of methods for production of Aβ protofibrils and antibodies that bind to these are disclosed in WO02/03911 and WO2005/123775.
Of special importance was the development of the mouse monoclonal antibody mAb158, an antibody that binds to Aβ protofibrils, which is disclosed in EP2004688, which comprises the following CDR sequences:
VH-CDR1:SEQ ID NO: 1SFGMH VH-CDR2:SEQ ID NO: 2YISSGSSTIYYGDTVKG VH-CDR3:SEQ ID NO: 3EGGYYYGRSYYTMDY VL-CDR1:SEQ ID NO: 4RSSQSIVHSNGNTYLE VL-CDR2:SEQ ID NO: 5KVSNRFS VL-CDR3:SEQ ID NO: 6FQGSHVPPT
The high affinity and selectivity of the humanized version of mAb158, BAN2401, makes it a very important candidate for use in therapy and/or prevention of Alzheimer's disease in particular, and it is presently subject to clinical trials in preparation for use as a pharmaceutical product. Characteristics of BAN2401 are described in EP2004688.
The efficacy of an antibody depends on several pharmacokinetic and pharmacodynamics factors, see e.g. Deng et al, Expert Opin. Drug Metab. Toxicol 8(2) (2012): p. 141-160; Boswell et al, Bioconjugate Chem. 21(2010): p. 2153-2163; Konterman, Current Opinion in Biotechnology 22 (2011): p. 1-9 and Igawa et al, mAbs 3:3 (2011): p. 243-252. Among these, extended serum half-life with increased systemic exposure often provides a considerable potential for improvements of significant therapeutic value. It also provides an opportunity for reduction of the dose which has systemic, important implications.